1. Field of the Invention
The invention pertains to the field of document scanners.
2. Description of the Related Art
A document scanner is an extremely desirable peripheral that computer users would like to have available on their computer, like a floppy disk drive, a printer, a modem or a multimedia sound card. While prices of document scanners for personal computers users are rapidly declining, document scanners have not yet realized their anticipated success due to lack of integration, difficulty of use and slow speed.
Scanner technology requires knowledge and mastery of numerous disciplines: monochrome image sensors, color image sensors, light sources, stepper motors, paper feeders, motion drive mechanisms, power supplies, host interfaces, image processing and document processing. The intense price competition for basic document scanner models from Asian manufacturers forces non-Asian companies to abandon investment in that area. Innovation suffers and advancement in document scanner technology lags. Only manufacturers of sophisticated, extremely fast, bulky and expensive high volume document scanners enjoy a healthy growth.
Existing scanner technologies are essentially controlled by software running on a microprocessor that cooperates with a host computer. Only expensive microprocessors can process high-resolution document information at high speed. Scanners for the consumer market are generally too slow to provide any user productivity gain.
Furthermore, there are several types of scanners, each scanner type being specifically designed for a specific purpose: monochrome, color, sheet-fed, flatbed, handheld, photo-print, photo-slide, SCSI host interface, printer port host interface, IEEE1284 parallel port host interface, serial port host interface, USB host interface, IEEE1394 FireWire host interface, among others. Development costs and time to market are therefore significant. Only scanner manufacturers that are fully committed to document scanner products can afford to be involved in document scanner developments. Manufacturers that wish to incorporate document scanner functions into other types of devices (multifunction peripherals, for example) in order to differentiate their products from those of the competition have experienced difficulties reaching their goal.
Furthermore, it is well known that keyboards are the limiting factor in the man-machine interface, and large sums of money are being invested in the field of voice recognition/activation. There is also significant potential for handwriting activation, where instructions are handwritten on a small piece of paper and then scanned through a small low cost scanner and interpreted by a suitable software application. People do not always have a computer on-hand to key-in instructions, or a microphone to speak instructions into, but pen and paper is universal.
It is, therefore, an object of the present invention to provide manufacturers of consumer scanners with an inexpensive, highly integrated and easy to integrate scanner controller.
It is another object of the present invention to provide manufacturers with a scanner controller that integrates all scanner control functions on a single piece of silicon, or is integrated on a low cost hybrid circuit, together with logic for other peripheral functions.
It is yet another object of the present invention to provide manufacturers with a scanner controller device that can readily be integrated in a wide variety of consumer electronics, such as VCRs, microwave ovens, to name a few.
It is a further object of the present invention to provide manufacturers with a scanner controller for devices other than personal computers that is easy to integrate into their existing products, is inexpensive and enables increased functionality.
It is yet another object of the present invention to provide a scanner controller which is compatible with all types of scanners, such as monochrome, color, sheet-fed, flatbed, handheld, photo-print, photo-slide, among others. Furthermore, it is a further object of the present invention to provide a scanner controller which is also compatible with a great many host interface standards, such as SCSI, printer port, IEEE1284 parallel port, serial port, USB, IEEE1394 FireWire, among others.
It is also an object of the present invention to provide a scanner controller which is equipped for handwriting activation, where instructions are handwritten on a small piece of paper and then scanned through a small low cost scanner and interpreted by a suitable software application.
In accordance with the above-described objects and those that will be mentioned and will become apparent below, the Universal Document Scanner Controller according to the present invention is a circuit that integrates all of the control functions that are required to operate all types of monochrome and color document scanners.
The Universal Document Scanner Controller according to the present invention is designed to totally operate on a single piece of silicon or a low cost hybrid circuit, in order to achieve extremely fast performance. The specialized functions are entirely performed by the controller, which considerably simplifies the overall circuitry necessary to operate the scanner. The controller circuit according to the present invention can be mass-produced at a very competitive price. Manufacturers that wish to integrate a document scanner into other types of devices such as printers, keyboards, computer cases, display monitors, etc. to differentiate their products can expect a significantly reduced time to market, a very high performing product, and an extremely competitive price.
According to an exemplary embodiment, the scanner controller for controlling a document scanner according to the present invention comprises:
an internal bus;
an image sensor control unit, the image sensor control unit controlling and acquiring image data from at least one image sensor;
a pixel correction unit, the pixel correction unit performing calibration correction at a rate that matches an input pixel rate;
a motor control unit, the motor control unit controlling at least one motor; and
a host interface unit, the host interface unit controlling communication between the scanner controller circuit and a host computer.
The image sensor unit, the pixel correction unit, the motor control unit and the host interface unit are each connected to the internal bus. An advantage of the above-defined scanner controller is that it is readily implemented on a single piece of silicon, a multichip circuit, or a single piece of silicon together with other added circuits.
The motors controlled by the motor control unit may be stepper motors and/or linear motors.
The host interface unit supports tightly coupled communication links between the scanner controller and a host computer, such as an ISA bus, an EISA bus, a PCI bus, a VL bus, Intel AGP Advanced Graphics Port, a CPU data bus or a CPU local bus. The host interface unit also supports a direct link between the scanner controller and the host computer, such as a Floppy disk bus, an ATA bus, an ATAPI bus, an IDE bus, a removable IDE bus, an EIDE bus, a PCMCIA Bus, a Card Bus or a direct connection to the host interface. The host interface unit also supports loosely coupled communication links between the scanner controller and the host computer, such as a Serial, Printer port, EPP, ECP, IEEE1284, USB, SCSI, IEEE1394, Ethernet, Intranet, Modem, ISDN, ATM, IrDA, AppleTalk, ADSL, HDSL, TCP/AIP, wired, wireless, public, private, secured or unsecured communication link. Additionally, the host interface unit supports the Plug and Play requirements and standard. Moreover, the host interface unit is capable of simultaneously supporting at least two communication links between the scanner controller and the host computer in order to achieve higher data throughput than is possible with a single communication link.
A clock generator unit may be connected to the internal bus, the clock generator providing all timing signals required by all internal functions and external functions of the scanner controller. A memory control unit may also be connected to the internal bus, the memory control unit providing and controlling an access to internal and external volatile and non-volatile memory. The memory control unit may include one or a plurality of the volatile and non-volatile memories.
According to another embodiment of the present invention, a packing unit may also be connected to the internal bus, the packing unit packing and encapsulating pixels to satisfy an ordering of bits, as required by a host computer application.
A light source control unit may also be connected to the internal bus, the light source control unit controlling an illumination of all light sources used in document scanners. The light source control unit may perform light source modulation for monochrome LED light sources, color LED light sources, CCFL Cold Cathode Fluorescent Light tubes, Electroluminescent screens and/or filament lamps. This light source control unit may also perform selection of color filters for filter-type color scanners and for color-drop-out-type scanner, and may control one or a plurality of external Digital to Analog Converter and associated power circuits to control illumination switch-on, switch-off and intensity modulation.
A general-purpose status and controls unit may be connected to the internal bus, the general-purpose status and controls unit monitoring and sending event signals. The scanner controller according to the present invention may also include a black-side removal unit connected to the internal bus, the black-side removal unit being capable of removing pixels that are unrelated to the scanned document.
An Anti-Skew Auto-Start control unit may be connected to the internal bus, the Anti-Skew Auto-Start control unit ensuring that an edge of the document that is inserted into the document scanner is perfectly aligned in a scanner input before enabling a scanning operation, to automatically scan the document without unacceptable skew.
The scanner controller may also include an adaptative thresholding unit connected to the internal bus, the adaptative thresholding unit being capable of distinguishing relevant features from a background in a conversion from gray level pixels to black and white pixels. An image enhancement unit may also be integrated within the scanner controller according to the present invention, and connected to the internal bus.
The scanner controller according to the present invention may also include an image enhancement unit, a compression unit, a pixel dithering unit, a pattern recognition unit, all connected to the internal bus, and carrying out image enhancement, compression, pixel dithering, and pattern recognition using public algorithms, licensed algorithms, derived algorithms or specially developed algorithms.
An up and down sampling unit may be connected to the internal bus, the up and down sampling unit being capable of performing up-sampling or down-sampling of pixels. A rotary encoder control unit may also be connected to the internal bus, the rotary encoder control unit providing all necessary inputs and processing logic for decoding signals delivered by at least one rotary encoder. A mouse control unit may be connected to the internal circuit, the mouse control unit controlling either a standard mouse or an equivalent pointing device, and interpreting displacements and button selections.
A core Central Processing Unit may alternatively be connected to the internal bus, the core Central Processing Unit operating with programmed instructions contained in memory, the core central Processing Unit being synthesized from a public domain or commercial ASIC module library that can be added to the scanner controller to perform auxiliary functions.
A power management unit may be connected to the internal bus, the power management unit minimizing power consumption of all circuits in the document scanner controlled by the scanner controller circuit. Power circuits may also be included in the Scanner controller according to the present invention, which power circuits directly control all power functions of the document scanner. In addition to the power circuits, communication circuits, graphics display control circuits, keyboard control circuits, printer control circuits, auxiliary processing circuits and input device control circuits may be included in the controller, to control a complete multifunction peripheral, a complete off-line or an on-line document scanning terminal.
According to an embodiment of the present invention, the pixel correction unit performs, at the input pixel rate, linear and non-linear pixel correction including offset, gain, gamma and temperature corrections.
According to an exemplary embodiment, the scanner controller is capable of controlling image sensors with multiple pixel clock rates, is capable of controlling monochrome and color image sensors which produce an optical resolution ranging from 100 dpi to 4800 dpi, and is capable of controlling at least one fast Analog to Digital Converter in order to acquire the image from at least one document image sensor. The at least one Analog to Digital Converter may be integrated onto the scanner controller, to acquire video signals and other analog signals. The scanner controller according to the present invention may also include at least one Digital to Analog Converter integrated onto the scanner controller, to produce analog control signals.
Additionally, the scanner controller according to the present invention is capable of simultaneously acquiring a video signal from a plurality of image sensors, each image sensor having a single video output, simultaneously acquiring a plurality of video signals from an image sensor having multiple video output signals, or simultaneously acquiring the plurality of video signals from a plurality of image sensors having multiple video output signals.
The scanner controller according to the present invention can control the multiplexing of analog signals together with video signals, including sensor temperature, motor temperature, motor speed and light intensity analog signals.
In one exemplary embodiment, the pixel correction unit is capable of recognizing bad pixels, the bad pixels being caused by image sensor failure or by dust particles stuck in front of sensitive elements. Upon detection of bad pixels, the pixel correction unit is capable of replacing them automatically by interpolation of neighboring pixels.